In an existent power bipolar transistor for power application use, SiC is used as a semiconductor material, and a collector layer, a base layer and an emitter layer are arranged, for example, as shown in FIG. 3. FIG. 3 as a typical example is a vertical cross sectional structural view of the device. On an n-type substrate 91, a collector layer 92 having a donor density of about 2.5×1015 cm−3, a base layer 93 having an acceptor density of about 3×1017 cm−3, and an emitter layer 95 having a donor density of about 1×1019 cm−3 are epitaxially grown. A mesa structure 103 having an emitter layer 95 and a base layer 93 is formed to the stack. Then, a base electrode 100 is formed by way of a base contact region 97 in which high doped acceptor is generated by ion implantation and activation annealing. Further, an emitter electrode 99 is disposed directly to the emitter layer 95 and a collector electrode 101 is disposed directly to the rear face of the n-type SiC substrate 91. Reference 98 shows an isolation region where acceptor ions are implanted for relaxing concentration of an electric field in the collector layer 92 to a second mesa structure 107 comprising the base layer 93 and the collector layer 92, reference 96 shows a surface passivation layer and 102 shows an upper layer electrode. A typical example of an existent power bipolar transistor structure for power application is shown in Solid-State Electronics vol. 46 pp. 567-572 (2002).
Further, an example of an arrangement for a drift layer, a gate layer and an anode layer in an existent power thyristor using SiC as a semiconductor material is as shown in FIG. 4. FIG. 4 as a typical example is a vertical cross sectional structural view of a device. On an n-type substrate 111, a drift layer 112 having an acceptor density of about 2×1014 cm−3, a gate layer 113 having a donor density of about 2×1017 cm−3 and an anode layer 115 having an acceptor density of about 1×1019 cm−3 are epitaxially grown. In the stack, a mesa structure 123 having the anode layer 115 and the gate layer 113 is formed. Then, a gate electrode 120 is formed by way of a gate contact region 117 where high doped donor is generated by ion implantation and activation annealing. Further, an anode electrode 119 is disposed directly to the anode layer 115, and a cathode electrode 121 is disposed directly to the rear face of the n-type SiC substrate 111. Reference 118 shows an isolation region where donor ions are implanted for relaxing concentration of an electric field in the drift layer 112 to a second mesa structure 127 having the gate layer 113 and the drift layer 112, and 116 shows a surface passivation layer and 122 shows an upper layer electrode. A typical example of existent power thyristor structure is shown in U.S. Pat. No. 5,539,217. Further, as an improved proposal, a method of forming a semiconductor region for suppressing recombination near the surface of the low doped emitter layer is shown in JP-A-2006-351621. The technique is to be described more specifically with relation to a subject to be solved by the present invention.